Vibration dampener



March 3, 1936. H. D. NEWHART VIBRATION DAMPENER Filed March 6, 19 53 2 Sheets-Sheet l 5 INVENTOR Mame yD. NEW/MB T ATTORNEY March 3, 1936. H. D. NEWHART VIBRATION DAMPENER Filed March 6, 1933 2 Sheets-Sheet 2 A TTORNE Y Patented Mar. 3, 1936 UNITED STATES VIBRATION DAMPENER Harry D. Newhart, San Anselmo, Calif., assignor of one-half to Robert N. Carson, Jr.

Application March 6, 1933', Serial No. 659,766

23 Claims.

This invention relates to vibration dampeners.

There were some attempts made in the past to provide motion-checking devices for holding the wheels of automobiles or other devices in their true path so as to prevent the transmission of wheel or other strains to the operating or steering mechanisms, but experiments show that the checking of motion in any manner heretofore known impedes the steering or hinders the movement of moving parts. Consequently, in attempts of this kind heretofore made ease of steering had to be sacrificed to remedy to a certain degree the vibration and shimmying.

The Wheel shimmying in the steering gear of automobiles, for instance, is a periodicallateral wobbling or shaking of the wheels due to some force that starts them to vibrate and further periodical impulses which tend to amplify these vibrations resulting in' a very pronounced shaking of the wheels which makes steering difficult. The danger of such vibration of wheels, especially at high speeds is well known. The hydraulic dash-pot type dampeners, used in some attempts heretofore made to reduce shimmying, introduces a direct resistance to the steering action, which is very troublesome and renders the quick maneuvering of the steering mechanism very diflicult. Other attempts for shimmying dampening relied upon the inertia of a mass to counter balance the tendency of vibration. In these inertia devices if the mass or weight is too small, then a quick vibration will start to swing it and in effect it will ultimately aggravate the vibration, and if the mass or weight is larger, then it pro- 33 duces a very material drag on the steering mechanism.

The primary object of the herein invention is to provide a vibration dampener which offers definite resistance to quick movement at a neutral or straight position,v and only to anextent required by the expected wheel shimmy, but which leaves the steering mechanism completely free to move.

Another object of the invention is to provide a device for checking. quick, jerky motion, in which a moving member and a stationary member are locked together in one position; said position corresponding to the true, path of movement of the vehicle or machine on which the device is used, means being provided to allow comparatively slow movement of the movingmember out of its locked position, yet positively prevent any movement at a rate above a predetermined speed of motion, the device being also adapted to leave themovingmember entirely free and unobstruct ed as soon as it is moved out of said initial position; the device relies in its operation on an arrangement of pressure chambers and bypass between the chambers; heat responsive means being provided to maintain a constant bypass 5 irrespective of temperature changes; and means being also provided to prevent the forming of foam bubble, or air pockets in said chambers by keeping the same filled at all times.

Other objects and advantages are to provide a shimmy dampener that will be superior in point of simplicity, inexpensiveness of construction, positiveness of operation, and in facility and com venience in use and in general efficiency.

While the invention is illustrated in this specification and the annexed drawings, primarily in the form considered the best for a steering gear of automobiles, it will be obvious that it has a much wider application, as it can be used on the controls of an airplane, steering gear of a boat or torpedo, and almost anywhere where any control or steering mechanism may be subjected to undesirable vibrations, therefore, it'isto be under stood that the invention is not limited to the form herein shown, because it may be embodied in other forms; and it is also to be understood that in'and by the claims following the description, it is desired to coverthe invention in whatsoever form it may be embodied.

The invention is clearly illustrated in the accompanying drawings, wherein I Fig. l is a fragmental plan view of the front portion of the running gear, showing the dampeningdevice applied.

Fig. 2 15a plane view of dampening device part of the cover, and upper elements being broken away exposing to view a portion of the interior of the device.

Fig. 3-is a detail view of the piston of the device, part of the hub being broken away to show the heat responsive bypass control.

Fig. 4 is a sectional view of the device, the section being taken substantially on the line 4-4 of- Figure 2, the piston of device being shown in elevation.

Fig. 5 is a cross sectional view of the device,- the section being taken on the line 5-5 of Figure 4, the lower part of the piston being shown in elevation.

Fig. 6 is a top'plan view of the device, moved out of its initial or neutral position, the device being shown without the reservoir, part of the cover plate being broken away.

Fig. 7 is a fragmental, perspective view of the casing, showing: the'journal block therein.

Ill

r is secured over a front axle 6 in any suitable manner, such as by the U bolts 1 of the leaf spring 8. A lever arm 9 of the device is connected by a connecting link I to a suitable lug I 2 on the non-rotating backing plate of the vehicle front wheel I3. Instead of the connection of the lever arm II to the front wheel I3, the same may be connected to the usual tie rod I4 of the steering gear of the automobile.

, Before the wheel- I3 can move out of its straight position, which is its normal true path, it has to move the lever arm 9, and the motion of the latter by the wheel I3 is not resisted by my dampening device, unless the tendency of motion is quicker, than steering speed, in which latter case the arm 9 resists the force practically as if it were locked in its initial position.

The dampener itself includes a casing I5 secured on the base plate 5 by screws I6, shown in Figure 5. The casing I5 is cylindrical and is open at itstop. A cover plate I'I covers the top of the casing I5 and is held in place by screws I8. In the casing I5 is a piston I9, the hub 2| of which is journaled between diametrically opposite jour nal blocks 22 formed in the casing I5. The bearing thus formed is located centrally in the casing I5 and allows the piston I9 to oscillate around its axis. Diametrically opposite wings or arms 23 extend from the piston hub 2| toward the periphery of the casing I5. It is to be noted that the arms 23 are shorter than the radius of the inner periphery of the casing I5 to allow the ends of the arms 23 to move freely in the casing I5 without any obstruction. The height of the piston hub 2| and the arms 23 fits snugly between the bottom of .the casing I5 and the lower face of the cover plate I! so that any fluid in the casing I5 can flow only around the outer ends of said arms 23.

The casing I5 is filled with a suitable fluid such as oil'. As the piston I9 is oscillated the arms 23 move freely in the oil, and the oil can flow around the. outer ends of the arms 23, hence there. is no resistance whatever to the oscillating movement of the piston I9.

A shaft 24 extends from the hub 2| of the piston I9 and the hub 26 of the lever arm 9 is fixed to the shaft 24, so that any turning movement of the lever arm 9 tends to rotate and oscillate the piston I9. In order to prevent the oscillation of the piston I9 out of its initial position, shown in Figure 2 opposite, flexible diaphragms 21 are secured in the casing I5, opposite the respective ends of the arms 23 when the latter are in the said initialor neutral position. Each diaphragm '21 consists of a spring leaf of the same height as that of the arms 23 so that no oil can pass over the top or below the diaphragms 21. The diaphragms 2! are held in place by pins 28, one at each end of each diaphragm 21. Each diaphragm is in a position to form a chord of the inner periphery of the casing I 5 midway between the positions of the 'journa'l'blocks 22.

The diaphragms 21 are tangential to the outer ends of the piston arms 23, and in the initial or neutral position of the piston I9 the outer ends of the arms 23 are in contact with the respective diaphragms, thereby normally preventing the passage of oil from one side of the arms 23 to the other. Thus the casing I5 is divided, by the Journal blocks 22 and by the arms 23 and diaphragms 21, into four chambers 29, one on each side of each arm 23. In the absence of any escape for the oil from the chambers 29 the piston I9 would be substantially fixed and looked in its neutral, initial position, as against normal expected vibration caused by shimmying and the like. In case of a severe action applying suddenly more force than the usual vibration, such as the force of shoving off from a curve the diaphragms 21 are then bent outwardly by the excessive pressure, allowing escapement of oil from one side of the arm 23 to the other side similarly to a safety valve. The diaphragms having workable clearances will allow oil in the rear thereof to escape out to the low pressure sides of the arms 23.

In order to provide limited escapement of the oil from chamber to chamber at all times a bypass is provided in the piston hub 2 I. The bottom of the piston hub 2| has a cylindircal extension 30 thereon which fits into a corresponding cavity 3| thereby to provide additional bearing. The extension 30 and the piston hub 2| are hollow. The inner end of the hollow portion of the hub 2| is formed into a conical valve seat 32, as shown in Figure 3. Passages 33 extend from the outside of the hub 2| to said valve seat 32. There is a passage 33 leading from each side of each arm 23 to the valve seat 32, which establish intercommunication between the chambers 29 through the hollow portion of the piston hub 2|. A valve 34 is slidably disposed in the hollow portion of the piston hub 2|. The valve 34 fits over the valve seat 32, and rests upon metal discs 36, which latter in turn rest upon the inner end of a plug 31. The outer end of the hollow portion of the hub 2| is internally threaded to hold the externally threaded plug 31 in place. The plug 31 and the discs 36 are so arranged that the valve 34 normally drops below the orifices 38 of the passages 33 and leaves the same entirely unobstructed.

The discs 36 are made of such material as to be sensitive to heat, and expand and contract readily. For instance, each disc 36 is made of two layers welded together at the edge, the layers having definite coeficients of' expansion, such as one layer of invar steel and another layer of brass. The bending or bulging caused by the unequal expansion of the layers in each disc moves the valve 34 upwardly. Both on the bottom of the valve 34 and on the top or inner end of the plug 31 is a cylindrical boss 39 of smaller diameter than that of the plug, against which the discs 36 bear. The discs 36 are of substantially the same diameter as that of the hollow of the hub 2 I. In this manner a heat responsive bypass regulation is provided, which is necessary to compensate for changes in the fluidity of the oil due to temperature changes.

I When the temperature of oil increases it is more viscous or fluid and flows fasterthrough the passage 33. But the heat also causes the discs'36 to expand and bend slightly thereby moving the valve 34 toward its valve seat 32 partially covering the orifices 38 of the passages 33. Thus the flow through the passages 33 is restrictedin accordance with the rise in temperature. On the other hand cooling of the oil will cause it is a pocket 4.1.

to flow slower, and the dropping ofthe temperature will also cause the contraction. of the'discs 36, hence the valve 34 will be allowed to drop away from its valve seat 32 and uncover the orifices 38, in. accordance with the lowering of oil temperature.

The above described heat responsive bypass regulation maintains a constant limit of oil. escapement from chamber to chamber. The sizes of the passages 33 are such that oil can not escape through them fast enough to take care of quick, jerky movements of the piston H], such. as the movement caused by shimmying; yet the escapement is sufficiently fast to allow the speed of piston oscillation caused by steering. Consequently the piston I9 is practically locked in its neutral or initial position against quick vibrations and shimmying movements, but does not offer any resistance to steering. This is especially true, because as soon as the steering movement moves the ends of the piston arms 23 out of contact with the diaphragms 21, the division into chambers 29 ceases and the, oil can freely move around the arms 23.

In order to facilitate the movement of the ends of the piston arms 23 into and out of contact with the diaphragms 21, and to prevent excessive friction therebetween, the ends of the piston arms 23, are formed into flared heads 40, with arcuate contact surfaces concentric with the inher periphery of the casing I5. In effect, this results in practically a one line contact between each arm. head and its diaphragm 21 at the tangent line. Certain wheels have a tendency to shimmy not only at straightaway position but also at a slight turn, in order to resist such vibration throughout the entire arc of possible shimmying, the heads 49 of the arms 23 are flared as heretofore stated. In view of the fact that the arc of such possible shimmying is different on various Wheels and tires the flare is formed of a width suitable to said possible are of action.

While the aforedescribed bypass passages 33 prevent foaming, and bubbles to a certain degree, it is also advisable to provide means for keeping the casing l5 filled at all times, and to com.- pensate for expansion and contraction of oil, and also to obviate the entrance of air and the forming of pockets in the body of oil in the casing l5. It is to be noted that the body of oil in the casing |5 is quiescent, and to prevent its motion the casing l5 should be kept filled. For this purpose I provide a reservoir cover 4| above thev cover plate IT. The reservoir cover 4| is an inverted cup internally threaded at its open bottom for engagement with the externally threaded end of the casing I5. In the closed top of the reservoir cover 4| is an opening covered by a plug 42, through which opening the entire dampener can be filled with oil.

In the top of each journal block 22 is formed a cavity 43. The cover plate covers these cavities 43. Apertures 44 through the cover plate provide openings for the oil to flow from the reservoir cover 4| into the cavities 43. From the bottom of the cavities 43 extend passages 46, as clearly shown in Figure 8. There are two such passages 45 leading from each cavity 43, downwardly, one toward each side of the journal block 22. At the lower end of each passage 46 The upper end of each pocket 41 is above the outlet end of the passage 46, and terminates in a valve seat 48, on which latter is positioned a check valve 49. While in the present instance thecheck valve '49 constltute'sa1ball valve seated by its own gravity, spring pressed or other'type check valves could be also used. Above the check valve 49 and in the side of the journal block 22 is an outlet 50 opening into a chamber 29. When there is no oil in the casing l5, or the pressure is reduced in the chambers 29 then the pressure of the oil from the reservoir cover 4| lifts the check valve 49 off its seat 48, and oil flows into the chambers 29. Other times the pressure in the chambers 29 keeps the ball valve 49 on its seat. In this manner the chambers 29 are automatically refilled, and the forming of air pockets or bubbles is positively obviated.

The cover plate H has a central sleeve 5| upwardly extended therefrom into the reservoir cover 4! and around the shaft 24. There are holes 52 on this sleeve 5|, and the inner diameter of the sleeve 5| between the holes 52 and the easing I5 is slightly increased to facilitate seepage of oil to the holes 52. There is also a groove 53 on the inner periphery of the sleeve 5| and at the holes 52. If expansion of oil or other causes of increased pressure in the chambers 29 necessitate expulsion of oil from said chambers 29, then the oil is forced into the comparatively small clearance between the top of the hub 2| and the cover plate I? and then out through the holes 52 into the reservoir cover 4|. After the oil contracts, or the cause of excessive pressure is eliminated the chambers 29 are refilled through the cavities 43, passages v46, pockets 41, and outlets 50 as heretofore described.

The shaft 24 extends through a hole 54 to the outside of the reservoir cover 4|. An absorbent, protective washer 59, of fibrous material is placed around the shaft 24 and over the hole 54, to allow air into the reservoir cover 4|, but prevent seepage of oil to the outside. The hub 26 of the lever arm 9 is disposed on this washer 56 and is held in place by a nut 51 which latter is on the threaded outer end of the shaft 24.

The joint, whereby the outer, bent end '58 of the arm 9 is connected to the link l| consists of an aperturcd rubber pad or socket 59 on the end of the link A cotter pin 6|, or the like, prevents the disengagement of the end. 58 of the lever arm 9 from disc 69. When due to misalignment or for other reasons a twisting force is applied to the lever arm 9 then the pad 59 is compressed by the bent end 58 of said lever arm 9 without allowing any looseness or play otherwise.

The connection 62 shown at the other end of the link Il may be also a rubber socket, or it may be a ball and socket joint as shown.

In operation the piston |9 is practically fixed and locked in its initial or neutral position, as against quick jerks, vibration or shimmy, because the oil cannot flow fast enough from chamber 29 to chamber 29 to allow any such quick movement. When turned at steering speed the arms 23 of the piston i9 force the oil to flow through the bypass passages 33 at sufficient rateof flow to allow unresisted turning of the piston l9 from its neutral or initial position, and thereafter the arms 23 move entirely free in the body of oil in the casing l5 without even any further bypass. On account of the flared heads 49 of the arms 23 shimmying is resisted during the beginning of the turn of the wheel until the Wheel is turned to an angle at which shimmying is improbable. On the other hand in case of excessively sudden shocking force such as the wheel hittingagainst a. curb and the like, the flexible .dlaphragms21 oil from the sides of arms 23 under pressure to the other sides of the arms 23. But the diaphragms 21 are not flexible enough to bend under normal vibration such as wheel shimmying.

Having thus described this invention, what I claim and desire to secure by Letters Patent is:

1. In a motion checking device, a stationary element, a moving element, a body of normally quiescent fluid, yieldable means coacting with said moving element to resist movement of the fluid only when the moving element is in an initial position relatively to the stationary element and to allow free movement of the fluid relatively to the moving element in other positions, thereby to cause said body of fluid to resist sudden movement of the moving element from said initial position, means to allow movement of said moving element from said initial position at a predetermined rate of motion, and heat responsive control means for said escapement means to regulate escapement according to the temperature of the fluid.

2. In a motion-checking device, the combination of elements movable with respect toeach other, a body of normally quiescent fluid, yieldable means on one element and being engaged by the other element to cause said fluid to act as a resistance between the elements in only one, initial position of said elements, and means to bypass a limited amount of said fluid to allow the relative movement of said elements from. said initial position at a limited rate of speed.

3. In a motion-checking device, the combination of elements movable with respect to each other, a body of normally quiescent fluid, yieldable means to cause said fluid to act as a resistance between the elements in only one, initial position of said elements, means to bypass a l mited amount of said fluid to allow the relative movement of said elements from said initial position at a limited rate of speed, and heat responsive control means for said escapement means to regulate escapement according to the temperature of the fluid.

4. In a motion-checking device the combinat'on of a casing, a piston movable within the casing, a body of normally quiescent fluid located in chambers on each side of the piston, and resiliently yieldable means engaged by the end of the piston to prevent the passage of the fluid from one side of the piston to the other in one position of the piston but allowing free flow of fluid around the piston in other positions.

5. In a motion-checking device the combination of a casing, a piston movable within the casing, a body of normally quiescent fluid located in chambers on each side of the piston, resiliently yieldable means to prevent the passage of the fluid from one sidelof the piston to the other in only one position of the piston but allowing free flow of fluid around the piston in other positions, and means to allow a limited escapement of the fluid from one side to the other side of the piston at all times to allow the initial movement of the piston out of said position at a limited rate of speed.

6. In a motion-checking device the combination of a casing, a piston movable within the casing, a body of normally quiescent fluid located in chambers on each side of the piston, resiliently yieldable means to prevent the passage of the fluid from one side of the piston to the other in only one position of the piston but allowing free flow of fluid around the piston in other positions,

piston, the free end of the arm being spaced from the wall of the casing to allow unobstructed movement of the piston in said body of fluid and a flexible diaphragm in the casing to be engaged by the free end of the piston arm in a certain position of the piston so as to prevent flow of fluid from one side of the arm to the other in said position thereby causing said fluid to resist piston movement out of said position.

8. In a device of the character described, a casing, a body of fluid in the casing, a piston movable in the casing, an arm formed on the piston, the free end of the arm being spaced from the wall of the casing to allow unobstructed movement of the piston in said body of fluid; a flexible diaphragm in the casing to be engaged by the free end of the piston arm in a certain position of the piston so as to prevent flow of fluid from one side of the arm to the other in said position thereby causing said fluid to resist piston movement out of said position, and

means to bypass a limited flow of fluid from one side of the piston to the other to bypass the fluid from the path of the piston when the piston is,

moved off said diaphragm with a limited speed of movement.

9. In a device of the character described, a casing, a body of fluid in the casing, a piston movable in the casing, an arm formed on the piston, the free end of the arm being spaced from the wall of the casing to allow unobstructed movement of the piston in said body of fluid; a flexible diaphragm in the casing to be engaged by the free end of the piston arm in a certain position of the piston so as to prevent flow of fluid from one side of the arm to the other in said position thereby causing said fluid to resist piston movement out of said position, and means to bypass a limited flow or fluid from one side of the piston to the other to bypass the fluid from the path of the piston when the piston is moved ofi said diaphragm with a limited speed of movement, and heat responsive means to automatically regulate said bypass.

10. In a device of the character described, a casing, a body of fluid in the casing, a piston movable in the casing, an arm formed on the piston, the free end of the arm being spaced from the wall of the casing to allow unobstructed movement of the piston in said body of fluid; a flexible diaphragm in the casing to be engaged by the free end of the piston arm in a certain position of the piston so as to prevent flow of fluid from one side of the arm to the other in said position thereby causing said fluid to resist piston movement out of said position, and means to bypass a limited flow or fluid from one side of the piston to the other to bypass the fluid from the path of the piston when the piston is moved off said diaphragm with a limited speed of movement, and a reservoir to hold a reserve body of fluid, means of connection between the casing and said reservoir to allow limited seepage under pressure from the former to the latter, and means to communicate the reservoir with the casing on the respective sides of the piston arm to refill the space thereat when pressure in said casing is reduced below a predetermined limit.

11.'In a device of the character described, a casing, a body of fluid in the casing, a piston movable in the casing, an arm formed on the piston, the free end of the arm being spaced from the wall of the casing to allow unobstructed movement of the piston in said body of fluid; a flexible diaphragm in the casing to be engaged by the free end of the piston arm in a certain position of the piston so as to prevent flow of fluid from one side of the arm to the other in said position thereby causing said fluid to resist pistonmovement out of said position, and means to bypass a limited flow of fluid from one side of the piston to the other to bypass the fluid from the path of the piston when the piston is moved off said diaphragm with a limited speed of movement, and heat responsive means to automatically maintain a constant rate of bypass under various temperature conditions.

12. In a motion-checking device, a casing, a normally quiescent body of fluid in a compression space in the casing, an oscillating piston in the casing being spaced from the inner periphcry of the casing for unobstructed movement in said space, yieldable means coacting with the free end of the piston to separate the compression space into separate chambers in one predetermined position of the piston so that the fluid in said separated chambers resists movement of the piston from said predetermined position, and means to bypass a limited amount of fluid from chamber to chamber from the path of the piston movement when the piston is moved at a limited rate of motion.

13. In a motion-checking device a stationary casing, a piston oscillatable in the casing, a plurality of wings on the piston, a body of fluid in the casing, the free ends of the wings of the piston being spaced from the inner periphery of the casing, diaphragms in the casing engageable by the free end of the respective wings in a one position only of the piston to divide the easing into a plurality of separate chambers, and means to establish a limited communication between the chambers for a predetermined escape of fluid from chamber to chamber as the piston is oscillated at a certain speed of motion.

14. In a motion checking device of the character described, the combination of a casing, a body of fluid in the casing, a piston oscillatable in the casing, the free end of the piston being spaced from the wall of the casing to allow unobstructed movement of the piston in said body of fluid, an abutment in the casing to be engaged by the free end of the piston in a certain position so as to prevent flow of fluid from one side of the piston to the other around said free end in said position thereby to resist piston movement out of said position, the end of said piston adjacent said abutment being arcuate, and said abutment being tangential to the arc of said piston end.

15. In a motion checking device of the character described, the combination of a casing, a body of fluid in the casing, a piston oscillatable in the casing, the free end of the piston being spaced from the wall of the casing to allow unobstructed movement of the piston in said body of fluid, an abutment in the casing tobe engaged by the free end of the piston in a certain position so as to prevent flow of fluid from one side of the piston to the other around said free end in said position thereby to resist piston movement out of said position, the end of said piston adjacent said abutment being arcuate, and said abutment being flexible and tangential to the arc of said piston end.

16. In a motion checking device of the character described, the combination of a casing, a body of fluid in the casing, a piston oscillatable in the casing, the free end of the piston being spaced from the wall of the casing to allow unobstructed movement of the piston in said body of fluid, an abutment in the casing to be engaged by the free end of the piston in a certain position so as to prevent flow of fluid from one side of the piston to the other around said free end in said position thereby to resist piston movement out of said position, the end of said piston adjacent said abutment being arcuate, said abutment being flexible and tangential to the arc of said piston end, and being arranged to form an auxiliary fluid chamber behind said abutment.

17. In a motion checking device of the character described, the combination with a casing having a. body of fluid therein, an element journalled in the casing tobe oscillatable therein, substantially diametrically opposite wings extended from said element, the free ends of said wings being spaced from the inner periphery of the casing to move freely in. said fluid, and substantially diametrically opposite abutments in the casing to be engaged by the ends of the respective wings in a certain position of said member to resist relative fluid and wing movements in said position.

'18. In a motion checking device of the character described, the combination with a casing having a body of fluid therein, an element journalled in the casing to be oscillatable therein, substantially diametrically opposite wings extended from said, element, the free ends of said wings being spaced from the inner periphery of the casing to more freely in said fluid, substantially diametrically opposite abutments in the casing to be engaged by the ends of the respective wings in a certain position of said member to resist relative fluid and wing movements in said position, and separating elements in the casing positioned substantially at right angles to the position of said abutments to separate from each other the chambers within which the opposed wings move.

19. In a motion checking device of the character described, the combination with a casing having a body of fluid therein, an element journalled in the casing to be oscillatable therein, substantially diametrically opposite wings extended from said element, the free ends of said wings being spaced from the inner periphery of the casing to move freely in said fluid, substantially diametrically opposite abutments in the casing to be engaged by the ends of the respective wings in a certain position of said member to resist relative fluid and wing movements in said position, separating elements in the casing positioned substantially at right angles to the position of said abutments to separate from each other the chambers within which the opposed wings move, and means to establish a limited communication between the chambers.

20. In a motion checking device of the character described, the combination with a casing having a body of fluid therein, an element journalled in the casing to be oscillatable therein,

substantially diametrically opposite wings extended from said element, the free ends of said casing to be engaged by the ends of the respective wings in a certain position of said member to resist relative fluid and wing movements in said position, separating elements in the casing positioned substantially at right angles to the position of said abutments to separate from each other the chambers within which the opposed wings move, means to establish a limited communication between the chambers, and temperature controlled means to automatically adjust said communication in accordance with the temperature of said fluid.

21. In a motion checking device a stationary casing containing a body of fluid, a plurality of pistons freely movable together in said body of fluid, means forrtransmitting force to said pistons to oscillate the pistons simultaneously, spaced elements on said casing so arranged that the elements'are contiguous with the respective pistons in only one initial position of the respective pistons and being adapted to prevent movement of fluid from one side of the respective pistons to the other in said initial position, and partitions in said casing disposed between said initial positions of the pistons so as to separate the casing into as many chambers as the numbers of pistons working in the casing, a reservoir to hold a reserve body of fluid, and means in said partitions to establish controlled one way communication from the reservoir to each of said chambers on either side of each partition.

, 22. In a motion checking device a stationary casing containing a body of fluid, a plurality of pistons freely movable together in said body of fluid, means for transmitting force to said pistons to oscillate the pistons simultaneously,v

spaced elements on said casing so arranged that the elements are contiguous with the respective pistons in only one initial position of the respective pistons and being adapted to prevent movement of fluid from one side of the respective pistons to the other in said initial position, and partitions in said casing disposed between'said initial positions of the pistons so as to separate the casing into as many chambers as the numbers of pistons working in the casing, said elements being positioned substantially intermediately between the respective adjacent partitions, a reservoir to hold a reserve body of fluid, andmeans in said partitions to establish controlled one way communication from the reservoir to each of said chambers on either side of'each partition.

23. In a motion checking device a stationary casing containing a body of fluid, a piston freely oscillatable in said fluid, means of connection be tween the piston and the moving element the motion of which is to be checked, an' element in the casing being met by the free end of said piston only on the initial position of the piston so as to prevent movement of fluid from one side of the piston to the other, the free end of the piston being in an arcuate sliding line contact with said element.

HARRY D. NEWHART. 

